Five million people are annually diagnosed with streptococcal pharyngitis, and 1200-1500 die annually from complications of group A streptococcal (GAS) infections in the United States alone. The over all goal of this projection is to understand the cellular and immunological reason that up to a third of children vigorously treated for pharyngitis continue to shed streptococci and why even more fail to develop a measurable immune response. Our in investigation will make use of a well-developed intranasal infection murine model to mimic infection of human tonsils. Preliminary results show that GAS have an efficient tropism for lymphoid tissue (NALT) beneath nasal passages of BalBc. Adoptive transfer of transgenic, naive ovalbumin specific CD4 T cells will be used to study the T cell based immune response in vivo following intranasal infection of mice with wild type and mutant strains of GAS that expresses the Ova antigen on their surface. Experiments will determine impact of infection on the antigen specific T cell response in NALT and other lymphoid organs.